This inventionn relates to an improved system for purifying drinking water.
Water purifying systems of the type with which the present invention is concerned act as fractionary stills. Stills boil impure water to separate the impurities from the water. Some impurities typically found in tap water boil at temperatures higher than water while other impurities boil at temperatures lower than water. A fractionary still boils impure water within a heating tank to the point of saturated steam, then transports the steam through a condenser which cools the steam to a liquid state. Since the impurities which boil at a higher temperature than water are not vaporized with the steam, they remain in the heating tank and are thus separated from the water. Additionally, any dissolved or undissolved solids or heavy metals which do not boil at all remain in the heating tank and are also separated.
The prior art condensers have typically consisted of stainless steel or aluminum tubing, bent in the form of a helix. Steam passing through the tubing is cooled to a liquid state by the forced convection of air passing over the tubing. One disadvantage of using metal tubing is that the tubing is not very hydrophobic. Condensed water accumulates on the inside of the tubing and actually insulates the steam from the cooling air. As a result, the efficiency of the condenser is reduced. Additionally, the overall cost of the condenser is relatively expensive since a fan or some other device must be provided for blowing air across the condenser to cool the steam.
Prior patents pertaining to the use of various types of plastic materials bonding together to form heat transfer devices include: U.S. Pat. No. 3,830,676 to Elkins; U.S. Pat. No. 4,118,946 to Tubin; U.S. Pat. No. 4,212,347 to Eastman; and U.S. Pat. No. 4,480,635 to Ostrovsky.